A mechanical pipe extender having multiple segments is shown in German Patent No. 2,611,702. In this prior art device, the segments are guided and attached by means of bronze ledges that are shaped like a "T" in cross-section, and conform with conically tapered ring grooves in a polyhedronally-shaped member.
This prior art pipe expander, however, has proven only partially satisfactory. One problem exists in the high expense associated with the production of the continuous, conical grooves. Other problems exist with the basic structure. For example, the construction causes weakening of the polyhedronally-preshaped member particularly on its thin end, and reduction in its available surface area for the resting or attachment of the displaceable segments. In accordance with the design of this prior art device, the displaceable segments possess protruding T-shaped edge portions for insertion into the corresponding recesses in the polyhedronally-shaped member, which frequently break when placed under high loads. Likewise, there is a danger that upon idle travel the segments will tilt between two work strokes, as a consequence of the influence of gravity, and cause the formation of a non-uniform or incomplete lubricating film. Also, particles of dirt can find their way into the gap produced by the tilting of the segments, and enter between the sliding surfaces, leading, when under load, to severe damage and inability to properly move the sliding surfaces and segments.
It is thus an object of the present invention to overcome the disadvantages possessed by the prior art device by the provision of a multi-segment mechanical pipe expander with a different conformation and shape for the slidable cooperation between the segments. It is a further object to provide an optimally large resting surface between the segments to allow for the handling of great loads while at the same time assuring dependable guidance, alignment and attachment.